MONDAY, June 2, 2014 (HealthDay News) -- A pill that blocks male hormone activity can improve survival and delay the need for chemotherapy in men with advanced prostate cancer, a new clinical trial has found.
Men who took a daily dose of the drug enzalutamide started chemotherapy nearly a year and a half later than men who received a placebo, even though their prostate cancer had spread to other parts of their bodies, said senior study author Dr. Tomasz Beer, deputy director of the Knight Cancer Center at Oregon Health and Science University.
"Generally speaking, you don't want chemotherapy. It's very unpleasant. With enzalutamide, we're able to delay the time to chemotherapy by 17 months, which is very significant for patients," Beer said.
The oral drug also improved survival by nearly a third compared with placebo.
The benefits of enzalutamide were so great that the independent committee overseeing the clinical trial ended it early so the men receiving placebo could be offered the drug, Beer said.
Researchers presented the findings Sunday at the American Society of Clinical Oncology meeting in Chicago. The study was also published simultaneously online in the New England Journal of Medicine.
The trial was funded by pharmaceutical companies Medivation and Astellas Pharma.
Prostate cancer is the second leading cancer killer of men in the United States, behind lung cancer. About one of every seven men will be diagnosed with prostate cancer in their lifetime, and it will kill one in every 36 men, according to the American Cancer Society.
Enzalutamide blocks the ability of male hormones, also called androgens, to bind with prostate cancer cells and fuel their growth.
The drug is already approved by the U.S. Food and Drug Administration for prostate cancer patients who have had chemotherapy, based on its ability to prolong their survival, Beer said. Researchers decided to see if enzalutamide could help men prior to chemotherapy, since it is an easy-to-take pill with fewer side effects than standard chemo.
The trial involved more than 1,700 men located across the globe. Researchers randomly assigned 872 to receive enzalutamide, and the other 845 to take a placebo.
One year into the study, two-thirds of enzalutamide patients showed no progression in their prostate cancer, compared with just 14 percent of patients in the placebo group.
Overall, the pill reduced the risk of death by 29 percent, researchers reported. Seventy-two percent of patients in the enzalutamide group were alive when the trial was halted. In the placebo group, 63 percent were alive at the end of the trial.
Men taking enzalutamide generally began chemotherapy more than two years -- an average of 28 months -- after the start of the clinical trial. The placebo group started chemotherapy around 10.8 months into the trial.
The medication also caused prostate-specific antigen levels to decline by at least half in 78 percent of the men assigned enzalutamide, compared with 3 percent of placebo patients. Doctors use high PSA levels to diagnose prostate cancer.
Side effects included high blood pressure, fatigue, back pain, constipation and joint pain.
"It's an incredibly well-tolerated drug that has some minor side effects," said Dr. Bruce Roth, a professor of oncology at Washington University School of Medicine in St. Louis. "Certainly, anything that can delay the onset of chemotherapy is a plus for patients. There are a number of patients where you're just not ready to pull the trigger on something as toxic as chemotherapy, if you can put it off."
Roth added that enzalutamide appears to work just as well as abiraterone, the only androgen-blocking medication currently approved by the FDA for use in pre-chemo prostate cancer patients. Abiraterone inhibits the body's ability to produce androgen.
"It's at least as good as and possibly has a greater magnitude in reduction of risk of death than abiraterone," Roth said.
Both drugs are expensive, costing $8,000 to $9,000 a month, Roth said.
Roth expects that FDA approval for using enzalutamide prior to chemotherapy could come fairly quickly. "It's a more streamlined process to have the label expanded, compared with a new drug submission," he explained.
Visit the U.S. National Cancer Institute for more on prostate cancer.
SOURCES: Tomasz Beer, M.D., F.A.C.P., deputy director, Knight Cancer Center, Oregon Health and Science University, Portland; Bruce Roth, M.D., professor, oncology, Washington University School of Medicine, St. Louis; June 1, 2014, New England Journal of Medicine, online; June 1, 2014 presentation, American Society of Clinical Oncology annual meeting, Chicago
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